1. Field of the Invention
The invention relates generally to electronic medical devices implanted within an animal or human body, and in particular the invention relates to fully implanted electronic medical devices including a telemetry communication mechanism.
2. Description of Related Art
Implantable electronic medical devices (IMD) often need to communicate with other devices, such as another IMD or an external device, such as for example, a monitoring system or programming console.
A telemetry communication system sends and receives information in a bidirectional mode. The system sends or receives commands to a separate device that might cause the separate device to alter its electronic or electro-mechanical performance, thereby controlling the device. The system may consist of hardware and software, sensors, a transmission protocol, and normally some form of a display, and possibly hardware and software capable of recording such interactions.
Telemetry systems can be implemented to acquire and transmit data from a remote implanted source to provide information about the implanted device and a user's activities.
It is desirable for physicians to exercise control over an IMD or to otherwise obtain information regarding the operational status of an IMD.
IMD's perform certain tasks to render treatment for various medical conditions. IMD's that are designed to include a remote control telemetry mechanism require that the device send and/or receive remote control telemetry commands. It is critical that the main electronic parts and power supply of the IMD are hermetically sealed within the shell of the IMD, in order to guard the subject's internal tissue from possible leakage of, or contact with, toxic components within the IMD and also prevent the incursion of internal bodily fluids into the shell of the IMD. The main electronic parts and power supply of IMD's are hermetically sealed in a hard-shell case, usually made of some form of metallic material, such as for example titanium. It is appreciated that the shell casing of the IMD may be formed of another suitable material.
Metallic compounds are effective materials for comprising the shell of an IMD because they are non porous, inert and highly durable. They are disadvantageous however because metals interfere or block remote telemetry signals going to and from the electronic receivers.
The medical device industry, as a whole, has been utilizing materials, such as titanium in the construction of shells for IMD's for their durability, inertness and air and fluid tightness for not only the protection of the various electronic parts that are being encased from a subject's bodily fluids, but also for the protection of the implant subject's tissue from being exposed to potentially toxic or otherwise harmful elements that may be associated with the implanted components within the IMD.
In such instances however, problems arise, since remote control commands are unable to be received or sent on a uniform basis to or from the electronic components encased within the metallic shell or case of the IMD.
Short and long term implant tests of prospective materials for IMD's have identified problems associated with using plastic especially when the implanted device includes an on-board power supply. The problems include, but are not limited to, porosity that may allow for the incursion of internal bodily fluids into the case, as well as, possible off-gassing issues that could alter the plastic shell's structural integrity.
The prior art includes various attempts to reduce or overcome interference in sending/receiving telemetry signals from implanted electronic medical devices. For example, U.S. Pat. No. 6,868,288 B2 (to Thomson) is a telemetry receiver for an implantable medical device (IMD) with an RF antenna coupled to a telemetry circuit that includes an out-of-band rejection filter comprising a thin film bulk acoustic resonator filter.
U.S. Pat. No. 8,160,705 B2 (to Stevenson et al.) provides for an EMI filter terminal assembly for an AIMD including a radio frequency (RF) telemetry pin antenna extending therethrough, including a conductive shield extending over a portion of the RF telemetry pin antenna in non-conductive relation with the telemetry pin, and conductively connected to a ground associated with the AIMD.
U.S. Pat. No. 8,527,060 B2 (to Amely-Velez et al.) teaches a shield that is configured to preserve telemetry communications between an AIMD in a patient and a telemetry wand when in an environment having high power electromagnetical interferers. The shield may include a plastic composition, include a shell including a wall that defines a volume and an opening in the shell. The volume may be configured to receive therein the telemetry wand such that the second and lateral sides of the telemetry wand face respective portions of the wall and the first side faces the opening in the shell.
U.S. Pat. Publ. No. 2012/0326886 A1 (to Herman et al.) discloses a telemetry head for communication with an implantable medical device comprises a telemetry antenna and a shield substantially surrounding at least a portion of the antenna, the shield having a coating comprising a ferromagnetic material applied to at least a portion of the shield, wherein the coating is configured to shield at least the portion of the telemetry antenna from electromagnetic interference fields while permitting telemetry signals to pass through the coating.
Thus, it is desirable to expose an antenna in an IMD to remotely broadcasted signals without subjecting the antenna to interference from the metallic shell of an IMD.